1. Field of the Invention
The present invention relates to a rolling apparatus for forming a wire made of a metal, a plastic, a ceramic material or the like to a desired sectional shape by using a plurality of pressure rolls.
2. Description of the Related Art
In Japanese Patent Publication No. 6-73687, the present inventor disclosed a wire rolling apparatus comprising a plurality of work rolls having grooves in their outer circumferential surfaces. A wire is inserted in a space formed by abutting the outer circumferential surfaces of the plurality of grooved work rolls against each other and aligning the grooves of the plurality of grooved work rolls with each other, and is rolled by driving the plurality of grooved work rolls. In this apparatus, the plurality of grooved work rolls serve as driven rolls. Backup rolls arranged almost diametrically opposite to the wire insertion space with respect to the grooved work rolls are pressed against the grooved work rolls, thereby transmitting the drive force. The center of each grooved work roll is offset from the center of the respective backup roll in a wire feed direction.
FIG. 1 is a perspective view showing an example of the rolling apparatus of the above publication. A frame 102 is mounted on the upper part of the front face of a rolling apparatus 100 shown in FIG. 1. In the frame 102, U-shaped open-ended portions are set to face each other from three directions, so that the frame 102 has an inverted Y-letter shape. A means for holding grooved work rolls is built on the central portion of the front surface of the frame 102. This means includes a knob 103 for adjusting the offset of the grooved work rolls. Backup rolls 101 are accommodated in an opening 104 of the frame 102 with movable blocks 105.
The grooved work rolls, although not shown in FIG. 1 as they are located at positions concealed by the means for holding them, abut against the backup rolls 101 within the opening 104. A wedge 106 is disposed between one side surface 104a of the opening 104 and one end face 105a of each movable block 105. The wedge 106 moves the corresponding movable block 105 to press the corresponding backup roll 101 against the corresponding grooved roll. A bolt 106a is mounted on the end portion of the wedge 106. When the bolt 106a is fastened, the wedge 106 enters the opening 104 to press against one end face 105a of the movable block 105, thereby moving the movable block 105.
To roll the wire with the rolling apparatus 100, first, the knob 103 is operated to adjust the offset of the grooved work rolls, and the positions of the wedges 106 are adjusted to move the movable blocks 105. This determines the magnitudes of the pressures of the backup rolls 101 against the grooved work rolls. The magnitudes of the pressures of the backup rolls 101 against the grooved work rolls must be adjusted to predetermined values in each backup roll 101. When the backup rolls 101 and the grooved work rolls are equidistantly, radially arranged as shown in FIG. 1, the pressures of the backup rolls 101 must be set equal to each other.
In the rolling apparatus 100 of the above publication, a force according to the pressure of the backup roll 101 against the grooved work roll acts on one side surface 104a of the opening 104. If the pressure is increased, a distortion tends to occur in this one side surface 104a and a wall portion around the opening 104. The position of the movable block 105 is thus shifted and the degree of abutment of the backup roll 101 against the outer circumferential surface of the grooved work roll changes. As a result, it is difficult to obtain a stable desired pressure and to roll the wire with high precision.
Since the pressures of the backup rolls 101 against the respective grooved work rolls are set to predetermined values by adjusting the positions of the respective movable blocks 105, it takes time to set the pressures of the backup rolls 101 against the respective grooved work rolls. Accordingly, it is difficult to roll the wire at a high throughput.